Here's a Microsoft "Q" (Q176512) article that talks about it.
The User <Domain\Username> Connected to Port <COM x> Has Been Disconnected...
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The information in this article applies to:
Microsoft Windows NT Server version 4.0
Microsoft Windows 95
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SYMPTOMS
When you attempt to establish a dial-up connection to a Routing and Remote Access Service (RRAS) server from a Microsoft Windows 95 Dial-Up Networking (DUN) client, you may be able to log on but you are disconnected within the first 20 seconds. When you check the System event log on the RRAS Server, the following event message is displayed:
Event ID : 20050
Source : Router
Description: The user <Domain>\<Username> connected to port <Com x> has been disconnected because the computer could not be projected onto the network.
If you try to use a Dial-Up Networking (DUN) connection to troubleshoot RRAS connectivity, it may not work, and it may generate the preceding error message. A Microsoft Windows NT-based computer that is using a DUN connection to connect to the RRAS computer generates an error message.
CAUSE
The DUN credentials that are being used on the Windows 95 client are the same as a Demand Dial interface on the RRAS server. This causes the RRAS Server to force IP address negotiation with the RAS client as if it were a router.
RESOLUTION
To work around this problem, you will need to do one of the following:
Re-create the Demand Dial interface using a different set of credentials.
-or-
Change the credentials of the DUN client so that they do not match any of the Demand Dial interfaces on the RRAS server. This can be done by editing the DUN connection and changing the logon user name.
